Which type of fields is documented to cause muscle contractions and visual light flashes?

Time varying magnetic fields (TVMF) are known to cause muscle contractions and visual light flashes, primarily due to their dynamic nature. Unlike static magnetic fields that maintain a constant intensity, time varying magnetic fields are characterized by changes in their strength or direction over time. This variation can induce electric fields within the body, leading to neuromuscular stimulation.

When these fields change rapidly, they can interact with nerve tissues and muscle fibers, resulting in involuntary muscle contractions. Moreover, the interaction of these changing fields with the retina can create the perception of visual light flashes, commonly referred to as "phosphenes."

The understanding of the effects of TVMF is critical in MRI practice, especially when considering safety protocols for patients and staff in the presence of strong magnetic fields. Awareness of these effects can help in mitigating risks, particularly for sensitive groups in the clinical environment.